Conventional styli are used on coordinate measuring machines in order, with the latter, to record the geometry of objects with high precision. To this end, the coordinate measuring machine has an arm to which the stylus is fastened, specifically via an adapter which is typically provided with a thread and from which the shaft and a typically spherical sensing end extend. The measuring machine arm is then moved with the stylus to the workpiece in order to generate a contact-indicating signal upon contact with the workpiece. The geometric dimensions of the workpiece can be determined in the process in that the location of the measuring machine arm during the generation of the contact-indicating signal is recorded at the same time.
Depending on the measuring task, different measuring methods are conventional, for example the point-by-point probing of the workpiece or scanning, in which the stylus is moved over the workpiece while it is in contact with the latter. In order to achieve high levels of accuracy, typically calibration is first of all carried out in that a known body is scanned with the stylus on the arm or known positions are approached therewith. Then, the same arrangement can be used to scan the workpiece. In this procedure, accurate measurements require that no changes to the arm or the sensing means occur between the calibration and the actual measurement of the workpiece.
However, these can occur, for example, when the sensing means changes gradually by probing the workpiece, for instance, because it is moved over the workpiece in continuous contact therewith (“scanning”) and is thus subject to abrasion at the front end, or material abraded from the workpiece collects at the tip; both of these scenarios clearly change the geometry of the sensing end and thus falsify measurements. In order to slow down this effect, although the styli are provided with different sensing tips at their front ends in contact with the workpieces, said sensing tips being particularly suitable for the workpiece to be measured in each case and often consisting of ruby, diamond or other, particularly hard materials, in practice, regular stylus exchange and replacement is nevertheless necessary.
However, measurement accuracy is reduced not only when the stylus is subject to gradual wear; changes can also be brought about simply by temperature fluctuations, for instance because the materials of the stylus expand by heating. In order to avoid such effects, if necessary, use is already made of styli which have a very low level of thermal expansion. In addition, styli with spacings of different lengths between the sensing tip and the arm of the coordinate measuring machine are used, wherein, depending on the measuring task, the shaft that determines the spacing can also be mounted perpendicularly on the adapter or at some other angle.
However, this requires regular exchange of styli because wear occurs and because the large number of workpieces of different shapes and different measuring tasks can make different configurations of the styli necessary, for instance with regard to the length of the shaft, the diameter or the shape of the sensing tip, the materials used for the sensing tip, and so on.
The styli therefore represent a tool part that is changed regularly and, if necessary, newly acquired, but which nevertheless needs to be manufactured precisely.
Therefore, the styli have to be produced cost-effectively. In this case, different techniques are used for connecting sensing-means parts. Thus, the threaded adapter and the shaft are often adhesively bonded, soldered or shrink-fitted; the sensing tip and the shaft, by contrast, are generally adhesively bonded or soldered. This location is particularly susceptible to mechanical damage.
Nevertheless, it is necessary to be able to transport the styli without any risk of damage to the user.
In order to transport the styli, screwable tubes are used, into which the finished styli can be inserted. In order to avoid damage as a result of the stylus moving in the transportation container, padding can be introduced into the tube. However, in this case, it is not possible to rule out a situation in which, for instance, the stylus end gets caught on the padding, damage occurs, etc.
Therefore, transportation packaging already exists in which a cavity is provided, soft ribs projecting towards the middle of said cavity in order to fix a received stylus at the shaft when the ribs bear against the shaft. The cavity structure having the ribs can be flapped away from the shaft such that the latter is exposed and the stylus can be grasped. Over these styli, which are thus fixed in a flexible manner, it is possible to place a hood, thereby protecting the styli for transportation. Corresponding transportation packaging for styli having shaft diameters of between 3 and 6 mm is obtainable, for example, from Rose-Plastik AG, Hergensweiler/Lindau under the name MicroBox.
In such arrangements, it is possible for mixups to occur for instance simply because finished styli are accidentally packaged wrongly after production. This risk increases, the more stylus variants that have sometimes only minor visual differences are produced.
It would be desirable to be able to at least partially satisfy at least some of the indicated requirements.